The present invention relates to oblique web multiple surface panels, in particular webbed double surface board panels of aromatic polycarbonates or webbed multiple surface board panels in general. These consist of at least two parallel panels joined together by webs extending in particular arrangements.
The most frequent of the known panels is the webbed double panel in which the webs extend perpendicularly to the plane of the panel at regular spaced apart distances so that, when viewed in cross-section, a row of adjacent rectangular chambers is formed.
Owing to the anisotropic character of such boards with respect to their flexural strength, other geometrical forms such as, for example, the so-called framework geometry such as marketed under the trademark DEGLAS and VEDRIL have been developed in particular for products fabricated of PMMA (polymethyl methacrylate).
In these geometrical forms, the webs enclose an angle of about 45.degree. with respect to the horizontal plane of the panel, thus providing for reduced tension forces and increased rigidity for a given weight per unit area due to improved transmission of transverse forces.
As a result of these measures, the supporting elements located between the two major parallel surfaces of the panel may be arranged further apart so that there is a saving in the amount of material necessary to form the supporting construction and a saving in the time required for its installation.
A construction similar to the PMMA framework geometries has not hitherto been realized for polycarbonate webbed panels.
The only known construction is a so-called X-board 16 mm in thickness in which two 45.degree. webs per chamber are incorporated in the geometry in addition to the vertical webs.
Due to the additional oblique webs, this board has a weight per unit area of 3.3 kg/m.sup.2, which is substantially higher than that of standard 16 mm PC webbed boards (about 2.7 to 3.0 kg/m.sup.2).
It is not possible simply to apply the geometries which have been found satisfactory for the production of PMMA boards to boards made of polycarbonates due to the differences in the properties of the materials (e.g. modulus of elasticity).
Under heavy loads, the boards buckle before the maximum load is reached.